Method of making ester-crosslinked chitosan support materials and products thereof

Abstract

Chitosan support material is crosslinked using a heat-induced, amidification reaction in non-aqueous solvent. Crosslinking is achieved by the use of dicarboxylic acids which form amide bonds with chitosan. The type and degree of crosslinking can be controlled to tailor mechanical strength, solubility, and functionality, of the resulting chitosan support material. Quaternization and/or cyclodextrin-modification functionalization of the chitosan beads can also be effected in addition to the crosslinking to produce separation materials with great versatility and utility. The invention is applicable to chitosan support materials of various solids contents and geometrical shapes such as beads, fibers, films, and adhesive coatings.

What is claimed is: 
     
       1. A method for forming crosslinked chitosan from chitosan support material containing water, comprising the steps, in this sequence, of: (a) replacing said water from said chitosan support material with a polar, non-aqueous organic fluid;   (b) combining said chitosan support material with a sufficient amount of dicarboxylic acid or acid anhydride thereof to form a chitosonium ion complex, wherein said dicarboxylic acid or acid anhydride thereof includes a polymerizable carbon-carbon double bond; and   (c) heating said chitosonium ion complex effective to drive off water via amidification reaction and crosslink said chitosan support material.   
     
     
       2. The method of claim 1, wherein step (c) comprises a first substep and a second substep, wherein said first substep comprises heating said chitosonium ion complex effective to form an intermediate product comprising a non crosslinked, monocarboxylic acid derivative of said chitosonium ion complex, and said second substep comprises heating said intermediate product effective to form a crosslinked chitosan complex. 
     
     
       3. The method of claim 2, wherein said chitosan support material has a shape selected from the group consisting of beads, films, and fibers. 
     
     
       4. The method of claim 1, wherein said chitosan support material comprises beads. 
     
     
       5. The method of claim 1, wherein said chitosan support material comprises spherical beads. 
     
     
       6. The method of claim 1, wherein said chitosan support material comprises chitosan polymers having amine sites, and said chitosan support material comprises a porous network structure having both an exterior surface and an internal surface, and wherein said amine sites on said chitosan polymers in said chitosan support material are reacted during said heating step at locations both on said internal surface and on said exterior surface. 
     
     
       7. The method of claim 1, wherein said polar non-aqueous organic fluid is selected from the group consisting of isopropyl alcohol, acetone, chloroform, tetrahydrofuran, dioxane, benzene, toluene, and xylene. 
     
     
       8. The method of claim 1, wherein said dicarboxylic acid or acid anhydride thereof is a compound selected from the group consisting of maleic acid, fumaric acid, itaconic acid, citraconic acid, maleic anhydride, itaconic anhydride, and citraconic anhydride. 
     
     
       9. The method of claim 1, wherein said crosslinked chitosan support material are beads having 1 to 3 wt. % solids and having an average particle diameter size greater than about 0.3 mm. 
     
     
       10. The method of claim 1, wherein said crosslinked chitosan support material are beads having 1 to 3 wt. % solids and having an average particle diameter size ranging from about 0.5 mm to about 2.0 mm. 
     
     
       11. The crosslinked chitosan support material product of the method of claim 1. 
     
     
       12. The crosslinked chitosan beaded product of the method of claim 4. 
     
     
       13. The crosslinked chitosan beaded product of the method of claim 10. 
     
     
       14. The method of claim 1, further comprising performing, after step (c), a step (d) comprising replacing said polar, non-aqueous organic fluid in said crosslinked chitosan support material with an aqueous fluid. 
     
     
       15. The method of claim 1, wherein said dicarboxylic acid or acid anhydride thereof is an α,β-unsaturated carbonyl compound.